Fullback Ben Hornby enhanced his claims for a NSW Country Origin jumper with a hat-trick in St George Illawarra's record 42-12 thumping of Cronulla in the National Rugby League derby at Toyota Park.

Hornby, believed to be in a two-way battle with Bulldogs custodian Luke Patten for the Country fullback role, crossed in the 19th, 61st and 67th minutes with selectors among the ground-record 22,302 spectators watching the game.

Hornby's dazzling display overshadowed the successful comeback from long-term injury of St George Illawarra's former Country, NSW and Australian Test prop Jason Ryles.

Ryles hadn't played since the third State of Origin match last year, but showed no sign of the two rounds of shoulder surgery that threatened to end his career at just 24.

The big front rower spent 46 minutes on the paddock in a major boost for selectors as the domestic representative season looms large.

The drubbing the Dragons handed out was a record win for the joint venture club over their arch-rival southern Sydney neighbours.

And it looked on from the outset with the Dragons racing to an 18-0 lead after just 19 minutes through unanswered tries to centre Mark Gasnier, interchange forward Tony Jensen and Hornby, all of which hooker Mark Riddell converted.

Cronulla replied in the 27th minute with a try to interchange forward Matt Bickerstaff off a lovely long ball from halfback Brett Kimmorley, who converted to have his team in the hunt at the break.

But winger Nathan Blacklock's 40m intercept try off a Kimmorley pass almost immediately after the break restored the Dragons' 18-point lead.

Replacement forward Sam Isemonger gave Sharks fans hope when he crashed over in the 46th minute, Kimmorley converting to reduce the deficit back to 12 points.

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